Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
  • G01L5/0052—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes measuring forces due to impact
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M13/00—Testing of machine parts
  • G01M13/02—Gearings; Transmission mechanisms
  • G01M13/028—Acoustic or vibration analysis
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M13/00—Testing of machine parts
  • G01M13/04—Bearings
  • G01M13/045—Acoustic or vibration analysis
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M15/00—Testing of engines
  • G01M15/04—Testing internal-combustion engines
  • G01M15/12—Testing internal-combustion engines by monitoring vibrations
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
  • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
  • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
  • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
  • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
  • G01P15/09—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by piezoelectric pick-up
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/02—Indexing codes associated with the analysed material
  • G01N2291/028—Material parameters
  • G01N2291/02827—Elastic parameters, strength or force

Definitions

• the present invention relates to an impact transmitting device which is used in impact monitoring operations . More particularly, the present invention relates to an apparatus for detecting and reporting mechanical impact events in reciprocating machines.
• an impact transmitting device for reciprocating machines is to detect free vibrations which are typically symptomatic of machine failure and to transmit the free vibration measurements in the form of an electrical signal. This electrical signal is received by an external logic solver which determines whether or not the reciprocating machine should be powered down.
• an impact transmitting device saves unnecessary waste caused by speculative preventative maintenance and increases the life-cycle of reciprocating machine components by alerting operators to early-stage development of harmful mechanical conditions. Such conditions may include loose rod nuts, loose bolts, excessive slipper clearance, worn pins, broken parts, liquid in the process, and rubbing.
• an impact transmitting device is mounted to a reciprocating machine such as a reciprocating compressor having a compressor cylinder assembly.
• the impact transmitting device detects mechanical impact events in or near the compressor cylinder assembly. The amplitude of each detected impact event is compared to a preset threshold level. If the amplitude of the impact event surpasses the threshold, then the impact event is counted as an "above-threshold impact event.” The number of above-threshold impact events that are counted by the impact transmitting device during a preset time window interval is reported to an external logic solver such as a programmable logic controller (“PLC”) or distributed control system (“DCS”) . The external logic solver compares the signal to a predetermined level of acceptable above-threshold impact events during the given time window.
• PLC programmable logic controller
• DCS distributed control system
• prior art impact transmitting devices offer the ability to detect and report useful mechanical impact data, it has been observed that these devices have at least two deficiencies.
• the impact transmitter devices that do allow these parameters to be manipulated must be adjusted by using software prior to installation of the device or by an experienced technical person.
• an impact transmitting device that functions as a single self-contained unit. Moreover, it would be desirable to have an impact transmitting device having a simple "field" adjustable impact threshold level for detecting above-threshold level impact events and a simple "field” adjustable time window interval during which these above-threshold level impact events are counted.
• apparatus for impact measurement and transmission for reciprocating machines.
• An impact transmitting device in accordance with the present invention provides for the detection and transmission of (1) the quantity of severe impacts during a time window interval, and (2) the severity of the impacts above a static threshold. This impact quantity and severity measurement is used to differentiate singular "nuisance alarm” impacts from repeat "machine failure” impacts.
• An impact transmitting device in accordance with the present invention further provides a single self-contained unit comprising a stainless steel housing which contains an impact accelerometer, a detector circuit, a measurement and timing circuit, a -20mA driver circuit, independent polarity circuit, and an electromagnetic impulse protection unit.
• An impact transmitting device in accordance with the present invention still further provides a field adjustable static threshold defining the severity of the impact, and a field adjustable reference time window interval.
• the variable severe impact level threshold allows an operator to isolate severe impacts from typical machine vibration.
• the variable time window interval allows an operator to synchronize the present invention with different machine speeds and to collect severe impact data over an appropriate time frame .
• An impact transmitting device in accordance with the present invention also provides functionality independent of the polarity of the power of a PLC or DCS.
• FIG. 1A is a side view of a preferred embodiment of the present invention illustrating a housing and a through-bolt used connect the housing to a reciprocating machine.
• FIG IB is a plan view of a preferred embodiment of the present invention illustrating an adjustor to regulate impact threshold level and an adjustor to regulate time window interval .
• FIG. 2 is a sectional view of a preferred embodiment of the present invention illustrating an impact transmitting device attached to a reciprocating compressor.
• FIG 3 is a schematic view of a preferred embodiment of the present invention illustrating electrical components and operating sequence.
• FIG. 4A is a representation of a mechanical vibration pattern.
• FIG. 4B is a representation of impact pulses associated with the mechanical vibration pattern of FIG. 4A that are above an established impact threshold level.
• FIG. 4C is a representation of a time window interval associated with the mechanical vibration pattern of FIG. 4A. Description of Specific Embodiment
• the term "operatively connected” is used to mean “in direct connection with” or “in connection with via another element.”
• the term “having an input” is understood to mean “having one or more inputs.”
• the term “having an output” is understood to mean “having one or more outputs.”
• a particular embodiment of the present invention includes an impact transmitting device 100 comprising a stainless steel housing assembly 101, a mounting base 102, a through-bolt 103, an input connector 104, an impact level threshold adjustor 105, and a time window interval adjustor 106.
• the housing assembly 101 contains the impact transmitter detecting, measuring, and transmitting electrical unit 300 (FIG. 3) . While the housing assembly 101 of the preferred embodiment of the present invention is fabricated from stainless steel, it is intended that the housing assembly can be fabricated from any durable material suitable for plant operating conditions.
• the through-bolt 103 is used to attach the mounting base 102 of the impact transmitting device 100 to a reciprocating compressor 200 having a cross-head 201 and a drive rod 202 moving a piston 203 through a cylinder 204.
• the impact transmitting device 100 is positioned on the cross-head 201 of the reciprocating compressor 200 such that the through-bolt 103 is perpendicular to the motion of the drive rod 202 and compressor piston 203 through the cylinder 204.
• the housing assembly 101 contains a sensing unit 301, a detector circuit 302, a measurement and timing circuit 303, a 4-20mA driver circuit 304, a independent polarity circuit 305, and an electromagnetic impulse protection unit 306.
• the a sensing element 301 comprises a piezo-crystal accelerometer 1 having an output la.
• the detector circuit 302 comprises a charge amplifier 2 having an input 2a and an output 2b; a comparator 3 having inputs 3a and 3b and an output 3c; and a monostable multivibrator 5 having an input 5a and an output 5b.
• the measurement and timing circuit 303 comprises a DC reference voltage source 4 having a many-turn resistor 4a and an output 4b; a counter 6 having inputs 6a and 6b and an output 6c; an astable multivibrator 7 having a many-turn resistor 7a and an output 7b; a control switch 8 having inputs 8a and 8b and an output 8c,• a time delay unit 9 having an input 9a and an output 9b; a digital memory 10 having write inputs 10a and 10b and an output 10c; a digital-to-analog converter 11 having an input 11a and an output lib; a summation device 12 having inputs 12a, 12b, and 12c and an output 12d; and a control switch 13 having inputs 13a and 13b and an output 13c.
• the 4- 20 mA driver circuit 304 comprises a voltage-to-current converter 14 having an input 14a and outputs 14b and 14c .
• the independent polarity circuit 305 comprises a diode bridge 15 and a diode 16.
• the electromagnetic protection unit 306 comprises protection unit 17, and terminals 18a and 18b.
• the output 2b of the charge amplifier 2 is connected to the first input 3a of the comparator 3.
• the second input 3b of the comparator 3 is connected to the output 4b of the DC reference voltage source 4.
• the DC reference voltage source 4 is regulated by a multi-turn resistor 4a to establish a threshold voltage 401. If the impact-dependent voltage present at the first input 3a of the comparator 3 is less than the threshold voltage 401 from the DC reference voltage source 4, then the comparator 3 generates an output of "logic zero.” However, if the impact-dependent voltage at the output 2b of the charge amplifier 2 exceeds the threshold voltage of the DC reference voltage source 4, then the output 3c of the comparator 3 is switched to "high level.”
• the output of the comparator 3 is connected to the input 5a of the monostable multivibrator 5.
• the monostable multivibrator 5 When the output 3c of the comparator 3 switches to "high level,” the monostable multivibrator 5 generates a single output pulse 402, called an "event.”
• the monostable multivibrator 5 is connected to the input 6a of the counter 6.
• the counter 6 counts the pulses received from the monostable multivibrator 5. This count represents the quantity of impacts producing voltage above the threshold established by the DC reference voltage source 4.
• the output 6c of the counter 6 is connected to the write input 10a of the digital memory 10.
• the multi-turn resistor 7a of the astable multivibrator regulates a time window interval 403 during which each above-threshold impact events 402 is counted.
• the time window interval 403 is normally equal to the time required for 12 to 20 reciprocations of a reciprocating machine shaft to occur, which is equivalent to 0.3 to 4.0 seconds, and
• the output 7b of the astable multivibrator 7 is connected to the input 8a of the control switch 8, to the input 9a of the time delay unit 9, and to the write input 10b of the digital memory 10.
• the astable multivibrator 7 causes the digital memory 10 to store the quantity of events that were counted during the current time window interval.
• the counter 6 is then reset through the time delay unit 9.
• the output 10c of the digital memory 10 is connected to the input 11a of the digital-to-analog convertor 11.
• the digital-to-analog converter 11 converts the digital value of the number of stored above-threshold impacts to an analog signal .
• the output lib of the digital-to-analog converter 11 is connected to the input 12b of the summation device 12.
• the output 12d of the summation device 12 is connected to the input 14a of the voltage-to-current convertor 14.
• the voltage-to-current converter 14 converts the voltage at the output 12d of summation device 12 to a current.
• the current produced by the voltage-to-current converter 14 is in direct proportion to the number of above-threshold impacts 400 that were detected and relayed as impact events 402 during the time window interval 403. The value of that current will range from 4 to 20 mA, where a current of 4 mA represents 0 events ("no impact") and a current of 20 mA represents 16 events. Each event is equivalent to 1 mA of current.
• the output 2b of the charge amplifier 2 is connected to the input 12a of the summation device to provide an AC signal which is proportional to the actual vibration level.
• the outputs 14b and 14c of the voltage-to-current converter 14 are connected to the inputs 18a and 18b of the PLC or DCS (not shown) via the diode bridge 15 and the electromagnetic impulse protection unit 17.
• the diode bridge 15 allows the circuit 300 to function independent from the polarity established by the power supply of the PLC or DCS.
• the electromagnetic impulse protection unit 17 shields the circuit 300 from potentially damaging energy spikes.
• the output of the DC reference voltage source 4 is connected to the input 8b of the switch 8.
• the output 8c of the switch 8 is connected to the input 13a of the switch 13.
• the output 13c of the switch 13 is connected to the input 12c of the summation device 12.
• the input 13b of switch 13 is operatively connected via the diode 16 to the voltage present on terminal 18b of the PLC or DCS.
• the switch 8 is closed during "time off" intervals 404 at the output 7b of the astable multivibrator 7.
• the switch 13 is closed when the polarity of the voltage on terminal 18b is positive. When the switch 13 is closed, impact threshold voltage and time window interval signals are included in the output 12d of the summation device 12.
• the independent polarity circuit 305 enables impact transmitter device to function independent of the polarity at the terminals 18a and 18b. Moreover, the field adjustments to the impact threshold level 401 and the time window interval 403 are accomplished by reversing the input connection 104 (FIGS. 1A and IB) to terminals 18a and 18b. In this "reverse polarity" mode, the impact transmitter device will continue to function while an oscilloscope and a meter, or a combination scopemeter, is used to view the vibration data as the adjustments 105, 106 (FIG. IB) are manipulated. While this reverse polarity mode is described with respect to an impact transmitter device, it is intended that a reverse polarity mode may be used to facilitate field adjustments of any 24mA loop powered device- - such as a vibration sensor.
• the present invention provides a 4-20 mA loop powered impact transmitter device that is self-contained and enables an operator of the device to easily make field manipulations of the impact threshold level and the time window interval .

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
• Reciprocating Pumps (AREA)
• Details Of Reciprocating Pumps (AREA)
• Transmitters (AREA)
• Forging (AREA)
• Vibration Prevention Devices (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 2001
  • 2001-12-18 AT AT01991410T patent/ATE371194T1/de not_active IP Right Cessation
  • 2001-12-18 US US10/025,930 patent/US6588279B2/en not_active Expired - Lifetime
  • 2001-12-18 WO PCT/US2001/049411 patent/WO2002050554A2/en not_active Ceased
  • 2001-12-18 DE DE60130140T patent/DE60130140D1/de not_active Expired - Lifetime
  • 2001-12-18 AU AU2002231133A patent/AU2002231133A1/en not_active Abandoned
  • 2001-12-18 EP EP01991410A patent/EP1344069B1/de not_active Expired - Lifetime

Non-Patent Citations (1)

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